Meta isn't even trying to get anything on Vision OS at all, I'm sure they have no interest or care about that until and unless it becomes a mass market product.
They don't want to be locked out of freedom to do what they want, and that's a primary motivation here it's true. But the obsessive focus on ad revenue that people assume they have is pretty far from their thoughts in the VR/AR space at this point. They have complete faith that being the dominant owner of the dominant platform that they think the future of computing will revolve around (I'm not arguing this, but I'm satisfied it's what Zuckerberg believes) will yield sufficient value to be worthwhile and they aren't worried about how it happens at this point.
They don't want to be locked out of freedom to do what they want, and that's a primary motivation here it's true. But the obsessive focus on ad revenue that people assume they have is pretty far from their thoughts in the VR/AR space at this point. They have complete faith that being the dominant owner of the dominant platform that they think the future of computing will revolve around (I'm not arguing this, but I'm satisfied it's what Zuckerberg believes) will yield sufficient value to be worthwhile and they aren't worried about how it happens at this point.